Support overriding CC, respect *FLAGS in fake-curl
Support overriding CC, respect *FLAGS in fake-curl

The shipped libraries (obviously) do not work on non-amd64 platforms,
and rebuilding without the correct compiler and flags does not work
on more complex setups such as ppc64 with 32-bit userland.  Make
the Makefile permit CC override while preserving the current default,
and use user-provided CFLAGS, CPPFLAGS and LDFLAGS.

pycurl/pycurl,pycurl/pycurl,pycurl/pycurl